In a magnetic disk drive, a head/slider flies at a very slight height (flying height) over a rotating magnetic disk. The head/slider is mounted to a suspension assembly and supported over the magnetic disk. The suspension assembly includes a load beam and a flexure assembly, and the flexure assembly includes a flexure tongue. The head/slider is mounted to the flexure tongue.
The suspension assembly is mounted to an actuator unit and moves rotationally over the magnetic disk. A structure in which the head/slider is mounted to the suspension assembly is called a head gimbal assembly (HGA). A magnetic head formed on the head/slider needs to be accurately positioned over a track during read/write operation. An error can occur when the head/slider is positioned over the track due to various manufacturing errors occurring in different components making up the magnetic disk drive or irregularity in behavior of an air bearing or the suspension assembly.
Accordingly, the flexure tongue performs, with respect to the magnetic disk, a flexible pivotal motion generally known as a pitch and roll motion or a gimbal motion, thereby compensating for the error. In order for the flexure assembly to properly perform this delicate pivotal motion, the spring constant thereof is set with accuracy and managed.
The HGA incorporated in the magnetic disk drive is retracted in the ramp mechanism while the magnetic disk stops its rotation. The magnetic disk drive needs to tolerate a larger external impact force during the retracted state (non-operating state) than during the operating state. When an acceleration is applied to the head/slider of the HGA by an impact force, the flexure assembly supporting the head/slider is displaced largely due to the mass of the head/slider. When the displacement exceeds a certain level, the flexure assembly is plastic-deformed and cannot perform a given pivotal motion. Therefore, the suspension assembly is usually provided with a mechanism, called a limiter, for limiting the displacement of the flexure tongue. The plastic deformation of the suspension assembly may occur not only due to an impact on the magnetic disk during non-operation but also due to the handling of the HGA in a manufacturing process.
Japanese Patent Publication No. 2006-53971 (“Patent Document 1”) discloses a limiter, formed on a flexure, which engages in a load beam when a flexure tongue is displaced. Disadvantageously, the limiter of such a structure requires the bending work of the flexure, which increases costs, and a space for the limiter is needed, which is not appropriate for miniaturization. Japanese Patent Publication No. 1998-69745 (“Patent Document 2”) discloses a technique for limiting the motion range of a flexure tongue by a tether portion which is a part of an insulating layer, in place of a mechanical impact motion limiter such as that disclosed in Patent Document 1. The flexure tongue is coupled to a flexure base by the tether portion formed linearly.
According to the technique described in Patent Document 2, since the linear tether portion couples the flexure tongue to the flexure base, it can be considered that upon slight displacement of the flexure tongue with respect to the flexure base, the tether portion suppresses the motion instantly. If the tether portion of such a structure is adopted as a limiter, it may affect the normal pivotal motion of the flexure tongue. The smaller the suspension assembly, the more affected the pivotal motion is.